The crystallization of starch.

Abstract

To 3 grams of wheat starch, ground according to the method of Alsberg and Perry, 100 cc. of distilled water was added at room temperature. This solution was centrifuged for 10 minutes and after removal of the precipitate, centrifuging was repeated twice. To one part of the amylose solution thus obtained two parts of 96 per cent alcohol was added the same afternoon and the precipitate with supernatant liquid was allowed to stand for about 3 weeks. In the second week to a part of the precipitate and liquid an equal volume of 96 per cent alcohol was added, giving an alcohol concentration of 80 per cent. After 3 weeks the precipitates were examined in alcohol under the microscope and were found to contain many spherocrystals. If alcohol is added in excess to the amylose solution a refractive myelin precipitate, consisting of smaller or larger irregular lumps, is formed. This myelin precipitate was later partly present as such but all gradations between amorphous masses and perfect spherocrystals could also be found. The latter consist of separate, very refractive radial needles attached to a central point or nucleus. The needles are about 1μ thick and up to 25μ long. The spherocrystal is formed by several or numerous needles. If the crystal is less perfect, lumps of the less refractive myelin precipitate are still present at its center, so that the needles project only half their length, or the top of the needle is not pointed but formed by a lump that is still amorphous, or the needle itself remains thick and less refractive than the perfect needle, with a more refractive axis in the center. The precipitate from 80 percent alcohol showed more numerous and more perfect spherocrystals than the precipitate from 64 per cent alcohol.